The government will next month clamp down on illegal foreign workers who may be staying in the country without proper working visas, the Justice Ministry said Monday.

The move comes as the number of illegal immigrants in South Korea remained high in recent years despite efforts by the authorities to bring the problem under control.

As of the end of June, 166,518 foreigners were overstaying their working visas, a modest decrease from 177,955 in 2009 and 168,515 in 2010, according to the authorities.

The ministry said 17 immigration offices under its wing will conduct the one-month crackdown together with the Ministry of Employment and Labor, the National Police Agency and the Korea Coast Guard.

The crackdown will be mainly centered on workplaces that employ illegal workers, residential areas near foreign labor-concentrated factory zones, employment agencies and construction sites or service providers, which tend to hire relatively cheaper laborers, according to the ministry.

The target sites were chosen because they are considered to compromise job opportunities for local job seekers in the low-income bracket or to give a rise to illicit sex service providers, the ministry noted.

In the tally of illegal foreigners, Chinese nationals accounted for the bulk of the undocumented workers with a total of 69,943. Chinese with Korean backgrounds accounted for 19,637 of that total.

Vietnamese workers represented the second biggest illegal labor group with a population of 16,873, followed by Thai people with 12,905. (Yonhap)